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An Actuator Failure Tolerant

Control Scheme for on UnderwaterRemotely Operated Vehicle

Guide:Vinod.B.R

Presented by,VISAKH.VM1 AEIRoll No 12

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CONTENTS

Introduction

Mathematical Model of the ROV

a) ROV Nonlinear Model

b) State Space ROV Model

Input Decoupling Transformation and Sliding Mode Control Design

a) General Caseb) ROV Case Study : The Nonlinear State Transformation

c) ROV Case Study : Sliding Mode Control Law

Fault Tolerant Control Scheme

Fault Detection : The Residual Generator Module

Fault Isolation

Control Reconfiguration

Simulation Results

References

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INTRODUCTION

What is an ROV?

What are the challenges?

Actuator Failure Tolerant Control Scheme Usual Modules

How this paper is organized?

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CONTENTS

Introduction




Input Decoupling Transformation and Sliding Mode Control Designa) General Case

b) ROV Case Study : The Nonlinear State Transformation




Fault Isolation


Simulation Results

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Mathematical Model of ROV

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M Vehicle mass

m - Addition mass

Iz - Vehicle inertia moment around the z axis

iz - Addition inertia moment

Mc Resistance moment of the cable.

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Forces produced by the cable traction corresponding to asubmarine current of velocity Vc with

L cable length

Tv - vehicle weight in the water

W - weight for unit length of cablew - water density

Cdc - drag coefficient of the cable

Dc cable diameter

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Rx and Ry are the drag forces along the x and y axes

Cdi drag coefficient of the ith side wall

Cri the packing coefficient

Si area of the ith side wall

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Md and Mr are the components of the drag torque around thez axis produced by the vehicle rotation and by the current

Cd drag coefficient of rotation

Cr - packing coefficient of rotation

S - equivalent area of rotation

d1,d2,d3 vehicle dimensions along xa, ya and za axes

cangle between x axis and the velocity direction of current

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Substituting (2) to (5) in (1),

where the coefficients pi are tied to the physicalcharacteristics of the vehicle as given in table 1.

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State Space ROV Model

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CONTENTS

Introduction




Input Decoupling Transformation and Sliding Mode ControlDesign

a) General Caseb) ROV Case Study : The Nonlinear State Transformation




Fault Isolation


Simulation Results

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Input DecouplingTransformation

What is sliding mode control?

General Case

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For the transformed system

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Theorem 3

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Which implies asymptotic vanishing of the tracking error.

In order to achieve sliding mode on (18) . The following

inequality needs to be imposed. It can

be fulfilled imposing separately v inequalities. Each

inequality gives

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ROV : Nonlinear StateTransformation

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Rewriting 9 by fixing kth thruster, uk is the input

Nonlinear change of coordinates

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Applying transformation one gets the following equation

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With k=1 we will get the following equation

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ROV: Sliding Mode Control Law

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The result in theorem3 will be applied here with k=1. Thecontrol law is aimed at solving the regulation problemfor z1,z2,z3 with respect to their references.

Define

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The achievement of sliding motion on (18)requires the following condition:

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The following control law for T2:

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CONTENTS

Introduction









Fault Isolation


Simulation Results

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1. A FD unit based on residual analysis

2. A FI unit monitoring the three decoupled sliding

surfaces, each of which is affected by a uniquethruster.

3. A supervisor, in charge of performing the controlreconfiguration among the available set of redundantinputs.

4. A robust sliding mode based control law designed on adecoupled model of the ROV.

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Abrupt Fault

Incipient Fault

Assumption:Only one of the four thrusters can undergo a

fault. i.e, multiple thruster faults cannot be admitted.

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CONTENTS

Introduction









Fault Isolation


Simulation Results

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Fault Detection: The ResidualGenerator Module

This module uses Structural Analysis.

X Subset of the unknown variables

K Subset of the known variables

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The CUSUM algorithm is chosen to design the decisionmodule of the failure detection system of the ROV.

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CONTENTS

Introduction









Fault Isolation


Simulation Results

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Fault Isolation

Sliding Mode Controller can be exploited to performfault isolation

If |si| 0 , then Ti is failed.

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CONTENTS

Introduction









Fault Isolation


Simulation Results

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Control is reconfigured by fixing the failed thruster and by

using the other three healthy actuators.

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CONTENTS

Introduction









Fault Isolation


Simulation Results

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Simulation Results

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Abrupt fault

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Incipient Fault

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References M. Blanke, H. Niemann, and T. Lorentzen, Structural analysisA case

study of the rmer satellite, in Proc. IFAC Safeprocess,Washington,DC, 2003.

V. Cocquempot, R. Izadi-Zamanabadi,M.Staroswiecki,andM.Blanke,Residual generation for the ship benchmark usingstructural approach,in Proc. UKACCInt. Conf. (Conf. Publ. 455), 1998,pp. 14801485.

V. Utkin, Sliding Modes in Control Optimization. Berlin,Germany:Springer Verlag, 1992.

Sliding Mode Control: Theory and Applications by ChristopherEdwards, and Sarah K. Spurgeon.

Applied Nonlinear Control by Jean-Jacques E.Slotine , and WeipingLi.

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